Tensile Adhesion Research Articles

Stress relaxation and improved fracture toughness of metal bonding using flexible monolith sheets and an epoxy adhesive

AbstractWhile epoxy resins exhibit excellent mechanical and insulating properties as well as excellent stability against heat and chemicals, epoxy adhesives also have drawbacks such as brittleness and stress concentration. Rubber-based materials are often added to epoxy adhesives to increase toughness, but they are sensitive to heat and moisture, limiting their effectiveness in harsh environments. In this study, we propose a new sheet-type adhesive consisting of a conventional liquid epoxy adhesive and an epoxy monolith sheet with internal continuous pores, using the advantageous properties of the flexibility and toughness of the epoxy monolith to avoid stress concentration. We evaluated the adhesion strength for metal bonding using the sheet-type epoxy adhesives via a lap-shear tensile adhesion test at various temperatures. The total destruction energy was also estimated via a tapered double cantilever beam test. Furthermore, a heat cycle adhesion test was conducted using two types of metallic materials with different coefficients of thermal expansion to elucidate the effect of the monolith sheet on the improvement of interfacial failure induced by stress concentration.

Adhesion-Related Phenomena of Stellite 6 HVOF Sprayed Coating Deposited on Laser-Textured Substrates.

The focus of this research is to examine the feasibility of using laser texturing as a method for surface preparation prior to thermal spraying. The experimental part includes the thermal spraying of a Stellite 6 coating by High Velocity Oxygen Fuel (HVOF) technology on laser-textured substrates. The thermal spraying of this coating was deposited both on conventional substrate material (low carbon steel) and on substrates that had been previously heat treated (nitrided steel). The properties of the coatings were analysed using scanning electron microscopy (SEM), optical microscopy (OM) and Raman spectroscopy. Adhesion was assessed through a tensile adhesion test. The results showed the usability of laser texturing in the case of carbon steel, which was comparable or even better than traditional grit blasting. For nitrided steel, the problem remains with the hardness and brittleness of the nitrided layer, which allows for the propagation of brittle cracks near the interface and thus reduces the adhesion strength.

Influence of Bond Coat Roughness on Adhesion of Thermal Barrier Coatings Deposited by the Electron Beam–Physical Vapour Deposition Process

Thermal barrier coatings (TBCs) are effective protective and insulative coatings on hot section components of turbine engines. The quality and subsequent performance of the TBCs are strongly dependent on the adhesion between the coating and the metal substrate. The adhesion strength of TBCs varies depending on the substrate materials and coating, the coating technique used, the coating application parameters, the substrate surface treatments, and environmental conditions. Therefore, the roughness of the substrate surface has a significant effect on the performance of the TBC system. In this work, the roughness and microstructure of the 7YSZ (7 wt.% yttria-stabilised zirconia) top coat under different bond coat roughness treatments were studied. The purpose of this paper was to investigate the influence of the roughness of the bond coat on the adhesion of 7YSZ TBCs prepared by the electron beam–physical vapour deposition (EB-PVD) process. The VPA (vapour phase aluminium) bond coat was deposited on Inconel 718 nickel superalloy substrate using the above-the-pack technique. The ceramic top coat was applied to the bond coat using the EB-PVD process. The dependence between the TBC coating roughness and the bond coat roughness was determined. Adhesion strength measurements were performed according to the ASTM C 633 standard test method. The highest adhesion value observed in the tensile adhesion tests was 105 MPa. However, it was not determined whether the surface roughness of the bond coat affects the adhesion of the 7YSZ top coat.

A novel multifunction of wearable ionic conductive hydrogel sensor for promoting infected wound healing

Conductive hydrogels have attracted widespread attention in applications of artificial biological tissues and ionic skin. Herein, a highly ionically conductive and biocompatibility hydrogels that integrate sensing, low swelling, and antimicrobial are prepared by the composition of chitosan (CS) chains, tannic acid (TA), polyacrylic acid (PAA), and metal cations. The hydrogels with high conductivity had tensile strain repeatable adhesion, wide strain detection, biocompatibility, and motion sensing capabilities. Particularly, in the aspect of hydrogel strain sensing based on ion conduction, it has high nonliearity (GF=2.05) with a large strain (20 %-1400 %), and excellent cycle stability. In addition, owing to the low-swelling effect and dipole-dipole interaction between the existence of free catechol groups of the zwitterionic group and TA in the zwitterionic sulfobetaine methacrylate (SBMA), the hydrogels display repeatable and controllable adhesiveness. Meanwhile, the covalent cross-linking between AA and SBMA synergistically enhances the mechanical properties of the hydrogels (169 kPa, 1474 %). Furthermore, as demonstrated in the L929 mouse wound infection model, the results indicated that the prepared hydrogel group had antimicrobial activity and reduced inflammation, thereby accelerating wound healing. The biocompatible and mutli-functional conductive hydrogels provide a new method for the design of novel type ionic skin device.

Strength Enhancement of Polyurethane Film by Solution Annealing.

Recently, polyurethane elastomer (TPU) has attracted more and more attention depending on its excellent optical, mechanical, and retreatment properties. The high strength of polyurethane has always been pursued, which can enable its application in more fields. In this work, an aliphatic polyurethane elastomer membrane (HRPU6) was successfully synthesized, and its strength was obviously improved by solvent annealing technology. The tensile strength and adhesion strength can reach 64.56 and 2.58 MPa, but 36.55 and 1.57 MPa only before solvent annealing, respectively. The impact strength of laminated glass based on HRPU has also been significantly improved after solvent annealing, confirmed through drop ball impact testing. It has been confirmed that the increase in strength of HRPU6 is attributed to the enhancement of hydrogen bonding and the improvement of the phase separation degree.

Mechanical performance of cold mix asphalt containing cup lump rubber as a sustainable bio-modifier

The road construction industry aims to contribute to the protection of already compromised environment. Cold mix asphalt (CMA) is a measure initiated by the road industry to protect the environment and preserve energy. Despite having additional benefits, CMA has attracted little attention due to its inferior performance. CMA's performance is enhanced using a sustainable binder bio-modifier, natural cup lump rubber (CLR) is one of them. This study evaluated the tensile properties, rutting, moisture susceptibility, and adhesion properties of CLR-modified CMA (CMA-CR). The tensile property was enhanced by 26% due to CLR modification. CMA-CR had excellent rutting resistance of less than 2 mm rut depth at 10,000 load cycles, showing 70% improvement compared with conventional CMA. Moisture susceptibility evaluation indicated that CMA-CR had tensile strength ratio (TSR) value of 104%, satisfying the minimum 80% requirement of AASHTO T283. It also retained more than 96% bitumen coating. The moisture damage resistance was improved by 12% and 10% in terms of TSR and stripping, respectively. The durability results revealed that the CMA-CR mixture prevented higher mass loss, representing 14% improvement compared with conventional CMA.

Micro tensile tester measurement of biomechanical properties and adhesion force of microtubule-polymerization-inhibited cancer cells

Both mechanical and adhesion properties of cancer cells are complex and reciprocally related to migration, invasion, and metastasis with large cell deformation. Therefore, we evaluated these properties for human cervical cancer cells (HeLa) simultaneously using our previously developed micro tensile tester system. For efficient evaluation, we developed image analysis software to modify the system. The software can analyze the tensile force in real time. The modified system can evaluate the tensile stiffness of cells to which a large deformation is applied, also evaluate the adhesion strength of cancer cells that adhered to a culture substrate and were cultured for several days with their adhesion maturation. We used the modified system to simultaneously evaluate the stiffness of the cancer cells to which a large deformation was applied and their adhesion strength. The obtained results revealed that the middle phase of tensile stiffness and adhesion force of the microtubule-depolymerized group treated with colchicine (an anti-cancer drug) (stiffness, 13.4 ± 7.5 nN/%; adhesion force, 460.6 ± 258.2 nN) were over two times larger than those of the control group (stiffness, 5.0 ± 3.5 nN/%; adhesion force, 168.2 ± 98.0 nN). Additionally, the same trend was confirmed with the detailed evaluation of cell surface stiffness using an atomic force microscope. Confocal fluorescence microscope observations showed that the stress fibers (SFs) of colchicine-treated cells were aligned in the same direction, and focal adhesions (FAs) of the cells developed around both ends of the SFs and aligned parallel to the developed direction of the SFs. There was a possibility that the microtubule depolymerization by the colchicine treatment induced the development of SFs and FAs and subsequently caused an increment of cell stiffness and adhesion force. From the above results, we concluded the modified system would be applicable to cancer detection and anti-cancer drug efficacy tests.

A Semi‐Interpenetrating Poly(Ionic Liquid) Network‐Driven Low Hysteresis and Transparent Hydrogel as a Self‐Powered Multifunctional Sensor

AbstractConductive hydrogels are gaining significant attention as promising candidates for the fabrication materials for flexible electronics. Nevertheless, improving the tensile properties, hysteresis, durability, adhesion, and electrochemical properties of these hydrogels remains challenging. This work reports the development of a novel semi‐interpenetrating network poly(ionic liquid) hydrogel named PATV, via the in situ polymerization of acrylamide, N‐[Tris(hydroxymethyl)methyl] acrylamide, and 1‐vinyl‐3‐butylimidazolium tetrafluoroborate. The density functional theory calculations reveal that the poly(ionic liquid) in the hydrogel network acts as physical cross–linking points to construct hydrogen‐bond networks. Furthermore, the hydrogen‐bond networks dissipate energy efficiently and quickly, and thus stress concentration and hysteresis are avoided. The prepared hydrogel has a low hysteresis (9%), high tensile properties (900%), fast response (180 ms), high sensitivity (gauge factor = 10.4, pressure sensitivity = 0.14 kPa−1), and wide sensing range (tensile range: 1–600%, compression range: 0.1–20 kPa). A multifunctional sensor designed based on the designed hydrogel enables real‐time, rapid, and stable response‐ability for the detection of human movement, facial expression recognition, pronunciation, pulse, handwriting, and Morse code encryption. Furthermore, the assembled triboelectric nanogenerator displays an excellent energy harvesting capability, thus highlighting its potential application in self‐powered flexible wearable electronic devices.

Bio-Inspired Interlocking Structures for Enhancing Flexible Coatings Adhesion.

The flexible protective coatings and substrates frequently exhibit unstable bonding in industrial applications. For strong interfacial adhesion of heterogeneous materials and long-lasting adhesion of flexible protective coatings even in harsh corrosive environments. Inspired by the interdigitated structures in Phloeodes diabolicus elytra, a straightforward magnetic molding technique is employed to create an interlocking microarray for reinforced heterogeneous assembly. Benefiting from this bio-inspired microarrays, the interlocking polydimethylsiloxane (PDMS) coating recorded a 270% improvement in tensile adhesion and a 520% increase in shear resistance, approaching the tensile limitation of PDMS. The elastic polyurethane-polyamide (PUPI) coating equipped with interlocking structures demonstrated a robust adhesion strength exceeding 10.8MPa and is nearly unaffected by the corrosion immersion. In sharp contrast, its unmodified counterpart exhibited low initial adhesion and maintain ≈20% of its adhesion strength after 30 d of immersion. PUPI coating integrated with microarrays exhibits superior resistance to corrosion (30 d, |Z|0.01HZ ≈1010Ωcm2, Rct≈108Ωcm2), cavitation and long-term adhesion retention. These interlocking designs can also be adapted to curved surfaces by 3D printing and enhances heterogeneous assembly of non-bonded materials like polyvinylidene fluoride (PTFE) and PDMS. This bio-inspired interlocking structures offers a solution for durably bonding incompatible interfaces across varied engineering applications.

The effect of photooxidation aging on the cohesion and interfacial adhesion behavior of epoxy asphalt with a composite acidic curing system based on molecular simulation

AbstractThis paper investigated the cross‐linking network structure of epoxy asphalt (EA) with the different ratio of composite curing agents, and further determined the effect of photooxidation aging on the tensile and interfacial adhesion behavior of EA with different cross‐linking network structures through molecular simulation. Based on the molecular models of EA and the interface model between EA and aggregate, the crosslinking network structural characteristics and tensile mechanical behavior were determined. The interfacial adhesion behavior and the mechanization were further studied. The results indicate that 20‐EA and 6‐EA have an epoxy resin cross‐linked network with uniform pore structure and phase distribution. 2‐EA showed a denser cross‐linking network and uneven aggregation phenomenon. Photooxidative aging alleviated the aggregation phenomenon. A dense cross‐linking network improved the tensile strength and the ability of tensile performance to resist photooxidation aging. The interface of EA‐quartz exhibited higher adhesion strength than EA‐calcite due to the closer distance and stronger nonbonding interactions between EA and quartz. The low anhydride content and photooxidation aging made EA approach to the aggregate interface, increasing nonbonding interaction and interfacial adhesion strength. In addition, quartz aggregates were more suitable for application in EA mixtures due to the higher interfacial adhesion strength and lower water sensitivity.

Avaliação do desempenho de argamassas autonivelantes utilizando resíduos de fosfogesso e cerâmica branca

Abstract This study investigates the properties of self-leveling subfloor mortar mixtures with natural and calcined phosphogypsum waste in the form of calcium sulfate called anhydrite and white ceramic, by replacing 50% of the mass of Portland cement CP II Z-32. The effects of using waste were evaluated in the fresh (initial fluidity, flow retention, regeneration time, setting time, and heat of hydration) and hardened (compressive and flexural tensile strength, density, water absorption, void ratio, linear shrinkage, and tensile adhesion strength) state. The optimized mixture at a 1:1.5 cement/sand ratio (by mass) with 50% white ceramic had a 32.66 ± 4.26 MPa compressive strength at 28 days, low shrinkage and heat of hydration, showing the best performance among the wastes studied. In the calcium sulfate mortars, the mixtures with anhydrite showed better results for compressive and flexural tensile strength and tensile adhesion strength, with the waste calcination being beneficial.

Polyurethane coatings modified with ladder‐like polysiloxane

AbstractIn this work, ladder‐like polyphenylsiloxane containing silanol groups was used for modification of polyurethane (PU) based on MDI and polypropylene oxide polyol. The obtained coatings have excellent mechanical performance and adhesion to steel. This improvement was confirmed through a combination of characterization techniques. The tensile strength and strength adhesion to steel increase by more than one order of magnitude when polysiloxane fraction increased from 10 to 50 wt.%. With an increase loading level, the coating transforms from hydrophilic to hydrophobic. The reinforcement effect was motivated by restriction of molecular mobility in PU matrix as was shown by solid‐state 1H NMR spectroscopy and formation of chemical bonds between PU and polysiloxane units.

Preparation and properties of organosilicon-polyurea composites

A series of organosilicon-polyurea composites were synthesized with hydroxy silicone oil (PDMS), coupling agent KH902, hexamethylene diisocyanate (HDI) and polyaspartate resin F420. The properties of the composites were characterized by tensile strength, adhesion, water absorption and thermogravimetric analysis. The effects of silicone modification conditions and silicone content on the properties of the composites were investigated. The results showed that the adhesion, water resistance and thermal stability of the composites were improved with the introduction of organosilicon. When the content of hydroxy silicone oil was 20%, the tensile strength of the composite was 37.614 Mpa, the elongation at break was 20.13%, the adhesion to cement mortar was 4.68 Mpa, and the water absorption was only 1.35%.

Application of Vietnamese Nano Graphene as SBR Rubber Reinforcement for Abrasion Resistance Conveyors

Graphene has been extensively considered as an ideal additive to improve the mechanical properties of many composite materials, including rubbers, because of its novel strength, high surface area, and remarkable thermal and electron conductivity. Styrene Butadiene Rubber (SBR) is considered a good material for abrasion resistance conveyors in industries. However, the mechanical properties of SBR still need to be improved. This study shows the enhancement of Vietnamese nano graphene (GNPs) on mechanical properties of SBR rubber such as tensile strength, tear strength, abrasion resistance, and adhesion strength. The distribution of the Dioctyl Phthalate (DOP)-modified GNPs in the SBR matrix was investigated using scanning electron spectroscopy. Results show a significant increase in SBR/GNPs nanocomposite mechanical properties with the presence of GNPs (tensile strength, and tear strength increased by 29.67% and 31.89% respectively in comparison with SBR rubber without GNPs, and abrasion weight loss was decreased by 30.84% in comparison with SBR and adhesion strength with polyester fabric was 3 times higher than that of SBR). The evaluation of GNPs content in SBR/GNPs nanocomposite material was carried out. Results show that 0.5 phr of GNPs content in SBR/GNPs nanocomposite material was the optimal GNPs content with good mechanical properties, high abrasion resistance, and good adhesion with polyester fabric.

Offset bending for interfacial toughness of plasma sprayed ceramic coatings

A modified three-point bending technique has been proposed to measure the interfacial toughness of thick plasma sprayed ceramic coatings. Four different ceramic materials (titania, yttria stabilized zirconia, alumina, and yttria) on steel substrate were investigated resulting in a range of toughness values. Plasma sprayed coatings were prepared on grit blasted substrates with two different roughnesses and subsequently a notch in the centre of the coated beam was fabricated using a SiC saw. A two-step three-point bend test was conducted: first, the notched sample was loaded with a small offset to create pre-crack. The pre-cracked specimens were further loaded with offset 0.5 to measure interfacial toughness. Crack propagation manifested as a pop-in in the load-deflection plot. Subsequently, finite element analysis was used to calculate interfacial toughness, Gc, corresponding to the pop-in load. The visualization of crack propagation after pop-in load suggested that the crack had propagated along the interface in all four coatings. The widely accepted tensile adhesion test (ASTM C633) was separately performed on the same four coatings to compare the results obtained from the offset bending test. A correlation between interfacial toughness measured using offset bending and adhesion strength measured using the tensile adhesion test has been proposed.

Evaluation of the Polymer Modified Tack Coat on Aged Concrete Pavement: An Experimental Study on Adhesion Properties

This study addresses the challenges of overlaying old concrete pavement with asphalt by introducing a new trackless tack coat material containing polymer. The aim is to enhance the durability of asphalt concrete overlay pavement on old cement concrete pavement. It contributes to the development of improved construction techniques for pavement rehabilitation and highlights the need for reliable adhesion performance evaluation based on different spray amounts and surface conditions. Additionally, to evaluate the effect of the adhesion performance based on the spraying amount, a tensile adhesion test was conducted by applying spray amounts of 0.30, 0.45, and 0.60 l/m2 on different surface conditions. The basic and adhesion performances of the polymer-modified tack coat material are evaluated through direct tensile and shear bond strength tests. The test outcomes demonstrated that the newly developed polymer-modified tack coat material had considerably greater adhesion strength compared to the traditional rapid-setting products. Its adhesive strength was 1.68 times higher on concrete and 1.78 times higher on asphalt. The new trackless tack coat material exhibited an adhesion performance of 1.05 MPa in direct tensile strength at 0.45 l/m2, which was 1.21 times higher than the rapid-setting tack coat. Results also confirmed that the new tack coat material exhibits values 1.90 times greater than the conventional rapid-setting tack coat material in shear bond strength, respectively. By simulating the process of separation and re-adhesion of pavement layers caused, the new tack coat material shows a tensile adhesion strength of 63% of the original state, which is advantageous for securing the durability of the pavement. Overall, the newly developed polymer-modified trackless tack coat has been shown to effectively enhance the adhesion performance between pavement layers without process delay, highlighting the potential of the new tack coat material to enhance the durability of asphalt concrete overlay pavement on old cement concrete pavement.

Assessment of Cementitious Ceramic Tile Adhesives in the Light of Repeatability and Reproducibility of the Tensile Adhesion Strength Measurements.

The paper presents the results of tensile adhesion strength measurements of ceramic tile adhesive (CTA) stored in various conditions performed by ten operators in one laboratory using the same equipment and auxiliary materials. The obtained results allowed the authors to estimate the repeatability and reproducibility of the tensile adhesion strength measurement method using the methodology following ISO 5725-2:1994+AC1:2002. Standard deviations of repeatability ranging from 0.09 to 0.15 for the general means value in the range of 0.89-1.76 MPa and standard deviations of reproducibility ranging from 0.14 to 0.21 for the same general means content indicate that the accuracy of tensile adhesion strength measurement method is not high enough. From the group of ten operators, five perform tensile adhesion strength measurements daily, the remaining five perform other measures, and the results obtained by professionals and non-professionals showed no significant differences. In light of the obtained results, compliance assessment with this method with the criteria set out in the harmonized standard EN 12004:2007+A1:2012 carried out by different operators may be divergent, and there is a significant risk of incorrect assessments. This risk is additionally increasing in the case of the evaluation conducted by market surveillance authorities, which use the simple acceptance rule that does not consider measurement variability.

Behaviour of masonry walls reinforced by fiber reinforced polymers

Masonry structures revealed their vulnerability to seismic loads through the damage sustained during the earthquake. Consequently, a problem with load transmission has arisen due to the failure of structural elements. To address this issue, various studies have been conducted to explore reinforcement or repair solutions aimed at enhancing the stability of damaged elements by increasing their resistance. Reinforcing a structure consists in improving the mechanical characteristics of the different elements that compose it. Choosing the accurate fiber reinforced polymers (FRPs) configuration to reinforce masonry walls increase the adhesion between the fiber reinforced polymer (FRP) and the wall subjected to the diagonal compression. The reinforcement system performance is mainly related to the quality of the adhesion between the masonry base and the material used for reinforcement. The assessment of the bonding quality is important and allows measurement of the tensile adhesion of FRP composites.

Alginate/polyacrylamide host-guest supramolecular hydrogels with enhanced adhesion

Although injectable hydrogels with minimally invasive delivery have garnered significant interest, their potential applications have been restricted by a singular property. In this study, a supramolecular hydrogel system with improved adhesion was constructed through host-guest interactions between alginate and polyacrylamide. The maximum tensile adhesion strength between the β-cyclodextrin and dopamine-grafted alginate/adamantane-grafted polyacrylamide (Alg-βCD-DA/PAAm-Ad, namely AβCDPA) hydrogels and pigskin reached 19.2 kPa, which was 76 % stronger than the non-catechol-based control hydrogel (β-cyclodextrin-grafted alginate/adamantane-grafted polyacrylamide, Alg-βCD/PAAm-Ad). Moreover, the hydrogels demonstrated excellent self-healing, shear-thinning, and injectable properties. The required pressure to extrude the AβCDPA2 hydrogel from a 16G needle at a rate of 2.0 mL/min was 67.4 N. As the polymer concentration and adamantane substitution degree increased, the hydrogels exhibited higher modulus, stronger network structure, and lower swelling ratio and degradation rate. Encapsulating and culturing cells within these hydrogels demonstrated good cytocompatibility. Therefore, this hydrogel can serve as a viscosity extender or bioadhesive, and as a carrier material to deliver encapsulated therapeutic substances into the body through minimally invasive injection methods.

On-Site Cross-Linking of Polyacrylamide to Efficiently Bind the Silicon Anode of Lithium-Ion Batteries.

Silicon anode suffers from rapid capacity decay because of its irreversible volume changes during charging and discharging. As one of the important components of the electrode structure, the binder plays an irreplaceable role in buffering the volume changes of the silicon anode and ensuring close contact between various components of the electrode. Traditional PVDF binder is based on weak van der Waals forces and cannot effectively buffer the stress coming from silicon volume expansion, resulting in rapid decay of silicon anode capacity. In addition, most natural polysaccharide binders with a single force face the same problem due to poor toughness. Therefore, it is extremely important to develop a binder with good force and toughness between the silicon particles. Herein, polyacrylamide (PAM) polymer chains that are premixed homogeneously with various components are cross-linked on-site on the current collector via the condensation reaction with citric acid, forming a polar three-dimensional (3D) network with improved tensile properties and adhesion for both silicon particles and current collector. The silicon anode with the cross-linked PAM binder exhibits higher reversible capacity and enhanced long-term cycling stability; the capacity remains at 1280 mA h g-1 after 600 cycles at 2.1 A g-1 and 770.9 mA h g-1 after being subjected to 700 cycles at 4.2 A g-1. It also exhibits excellent cycle stability in silicon-carbon composite materials. This study provides a cost-effective binder engineering strategy, which significantly enhances the long-term cycle performance and stability of silicon anodes, paving the way for large-scale practical applications.